#include "MemoryTracker.h"

#include <IO/WriteHelpers.h>
#include "Common/TraceCollector.h"
#include <Common/CurrentThread.h>
#include <Common/Exception.h>
#include <Common/formatReadable.h>
#include <common/logger_useful.h>

#include <atomic>
#include <cmath>
#include <random>
#include <cstdlib>


namespace DB
{
    namespace ErrorCodes
    {
        extern const int MEMORY_LIMIT_EXCEEDED;
    }
}


static constexpr size_t log_peak_memory_usage_every = 1ULL << 30;

MemoryTracker total_memory_tracker(nullptr, VariableContext::Global);


MemoryTracker::MemoryTracker(VariableContext level_) : parent(&total_memory_tracker), level(level_) {}
MemoryTracker::MemoryTracker(MemoryTracker * parent_, VariableContext level_) : parent(parent_), level(level_) {}


MemoryTracker::~MemoryTracker()
{
    if ((level == VariableContext::Process || level == VariableContext::User) && peak)
    {
        try
        {
            logPeakMemoryUsage();
        }
        catch (...)
        {
            /// Exception in Logger, intentionally swallow.
        }
    }
}


void MemoryTracker::logPeakMemoryUsage() const
{
    const auto * description = description_ptr.load(std::memory_order_relaxed);
    LOG_DEBUG(&Poco::Logger::get("MemoryTracker"), "Peak memory usage{}: {}.", (description ? " " + std::string(description) : ""), ReadableSize(peak));
}

void MemoryTracker::logMemoryUsage(Int64 current) const
{
    const auto * description = description_ptr.load(std::memory_order_relaxed);
    LOG_DEBUG(&Poco::Logger::get("MemoryTracker"), "Current memory usage{}: {}.", (description ? " " + std::string(description) : ""), ReadableSize(current));
}


void MemoryTracker::alloc(Int64 size)
{
    if (blocker.isCancelled())
        return;

    /** Using memory_order_relaxed means that if allocations are done simultaneously,
      *  we allow exception about memory limit exceeded to be thrown only on next allocation.
      * So, we allow over-allocations.
      */
    Int64 will_be = size + amount.fetch_add(size, std::memory_order_relaxed);

    if (metric != CurrentMetrics::end())
        CurrentMetrics::add(metric, size);

    Int64 current_hard_limit = hard_limit.load(std::memory_order_relaxed);
    Int64 current_profiler_limit = profiler_limit.load(std::memory_order_relaxed);

    /// Cap the limit to the total_memory_tracker, since it may include some drift.
    ///
    /// And since total_memory_tracker is reseted to the process resident
    /// memory peridically (in AsynchronousMetrics::update()), any limit can be
    /// capped to it, to avoid possible drift.
    if (unlikely(current_hard_limit && will_be > current_hard_limit))
    {
        Int64 total_amount = total_memory_tracker.get();
        if (amount > total_amount)
        {
            set(total_amount);
            will_be = size + total_amount;
        }
    }

    std::bernoulli_distribution fault(fault_probability);
    if (unlikely(fault_probability && fault(thread_local_rng)))
    {
        free(size);

        /// Prevent recursion. Exception::ctor -> std::string -> new[] -> MemoryTracker::alloc
        auto untrack_lock = blocker.cancel(); // NOLINT

        std::stringstream message;
        message << "Memory tracker";
        if (const auto * description = description_ptr.load(std::memory_order_relaxed))
            message << " " << description;
        message << ": fault injected. Would use " << formatReadableSizeWithBinarySuffix(will_be)
            << " (attempt to allocate chunk of " << size << " bytes)"
            << ", maximum: " << formatReadableSizeWithBinarySuffix(current_hard_limit);

        throw DB::Exception(message.str(), DB::ErrorCodes::MEMORY_LIMIT_EXCEEDED);
    }

    if (unlikely(current_profiler_limit && will_be > current_profiler_limit))
    {
        auto no_track = blocker.cancel();
        DB::TraceCollector::collect(DB::TraceType::Memory, StackTrace(), size);
        setOrRaiseProfilerLimit((will_be + profiler_step - 1) / profiler_step * profiler_step);
    }

    std::bernoulli_distribution sample(sample_probability);
    if (unlikely(sample_probability && sample(thread_local_rng)))
    {
        auto no_track = blocker.cancel();
        DB::TraceCollector::collect(DB::TraceType::MemorySample, StackTrace(), size);
    }

    if (unlikely(current_hard_limit && will_be > current_hard_limit))
    {
        free(size);

        /// Prevent recursion. Exception::ctor -> std::string -> new[] -> MemoryTracker::alloc
        auto no_track = blocker.cancel(); // NOLINT

        std::stringstream message;
        message << "Memory limit";
        if (const auto * description = description_ptr.load(std::memory_order_relaxed))
            message << " " << description;
        message << " exceeded: would use " << formatReadableSizeWithBinarySuffix(will_be)
            << " (attempt to allocate chunk of " << size << " bytes)"
            << ", maximum: " << formatReadableSizeWithBinarySuffix(current_hard_limit);

        throw DB::Exception(message.str(), DB::ErrorCodes::MEMORY_LIMIT_EXCEEDED);
    }

    updatePeak(will_be);

    if (auto * loaded_next = parent.load(std::memory_order_relaxed))
        loaded_next->alloc(size);
}


void MemoryTracker::updatePeak(Int64 will_be)
{
    auto peak_old = peak.load(std::memory_order_relaxed);
    if (will_be > peak_old)        /// Races doesn't matter. Could rewrite with CAS, but not worth.
    {
        peak.store(will_be, std::memory_order_relaxed);

        if ((level == VariableContext::Process || level == VariableContext::Global)
            && will_be / log_peak_memory_usage_every > peak_old / log_peak_memory_usage_every)
            logMemoryUsage(will_be);
    }
}


void MemoryTracker::free(Int64 size)
{
    if (blocker.isCancelled())
        return;

    std::bernoulli_distribution sample(sample_probability);
    if (unlikely(sample_probability && sample(thread_local_rng)))
    {
        auto no_track = blocker.cancel();
        DB::TraceCollector::collect(DB::TraceType::MemorySample, StackTrace(), -size);
    }

    if (level == VariableContext::Thread)
    {
        /// Could become negative if memory allocated in this thread is freed in another one
        amount.fetch_sub(size, std::memory_order_relaxed);
    }
    else
    {
        Int64 new_amount = amount.fetch_sub(size, std::memory_order_relaxed) - size;

        /** Sometimes, query could free some data, that was allocated outside of query context.
          * Example: cache eviction.
          * To avoid negative memory usage, we "saturate" amount.
          * Memory usage will be calculated with some error.
          * NOTE: The code is not atomic. Not worth to fix.
          */
        if (unlikely(new_amount < 0))
        {
            amount.fetch_sub(new_amount);
            size += new_amount;
        }
    }

    if (auto * loaded_next = parent.load(std::memory_order_relaxed))
        loaded_next->free(size);

    if (metric != CurrentMetrics::end())
        CurrentMetrics::sub(metric, size);
}


void MemoryTracker::resetCounters()
{
    amount.store(0, std::memory_order_relaxed);
    peak.store(0, std::memory_order_relaxed);
    hard_limit.store(0, std::memory_order_relaxed);
    profiler_limit.store(0, std::memory_order_relaxed);
}


void MemoryTracker::reset()
{
    if (metric != CurrentMetrics::end())
        CurrentMetrics::sub(metric, amount.load(std::memory_order_relaxed));

    resetCounters();
}


void MemoryTracker::set(Int64 to)
{
    amount.store(to, std::memory_order_relaxed);
    updatePeak(to);
}


void MemoryTracker::setOrRaiseHardLimit(Int64 value)
{
    /// This is just atomic set to maximum.
    Int64 old_value = hard_limit.load(std::memory_order_relaxed);
    while (old_value < value && !hard_limit.compare_exchange_weak(old_value, value))
        ;
}


void MemoryTracker::setOrRaiseProfilerLimit(Int64 value)
{
    Int64 old_value = profiler_limit.load(std::memory_order_relaxed);
    while (old_value < value && !profiler_limit.compare_exchange_weak(old_value, value))
        ;
}


namespace CurrentMemoryTracker
{
    using DB::current_thread;

    void alloc(Int64 size)
    {
        if (auto * memory_tracker = DB::CurrentThread::getMemoryTracker())
        {
            current_thread->untracked_memory += size;
            if (current_thread->untracked_memory > current_thread->untracked_memory_limit)
            {
                /// Zero untracked before track. If tracker throws out-of-limit we would be able to alloc up to untracked_memory_limit bytes
                /// more. It could be useful to enlarge Exception message in rethrow logic.
                Int64 tmp = current_thread->untracked_memory;
                current_thread->untracked_memory = 0;
                memory_tracker->alloc(tmp);
            }
        }
    }

    void realloc(Int64 old_size, Int64 new_size)
    {
        Int64 addition = new_size - old_size;
        addition > 0 ? alloc(addition) : free(-addition);
    }

    void free(Int64 size)
    {
        if (auto * memory_tracker = DB::CurrentThread::getMemoryTracker())
        {
            current_thread->untracked_memory -= size;
            if (current_thread->untracked_memory < -current_thread->untracked_memory_limit)
            {
                memory_tracker->free(-current_thread->untracked_memory);
                current_thread->untracked_memory = 0;
            }
        }
    }
}

DB::SimpleActionLock getCurrentMemoryTrackerActionLock()
{
    auto * memory_tracker = DB::CurrentThread::getMemoryTracker();
    if (!memory_tracker)
        return {};
    return memory_tracker->blocker.cancel();
}